A simple method for determining the resolving power of low resolution mass spectrometers (specifically quadrupoles) has been developed. The method can be used in all types of mass spectrometers and with different inization techniques (electron impact, chemical ionization, field ionization, particle induced ionization, etc.). The inlet system for DCB and DBB has been designed. Decachlorobiphenyl and decabromobiphenyl are used in this method as reference compounds to determine the resolving power of the mass spectrometer. These compounds can also be used for high mass sensitivity test on quadrupole mass spectrometers.